1. Field of the Invention
The present invention relates to an insulating structure for a shielded connector which reduces noise, for example, in an electric car, and particularly relates to an improvement of insulation between a metal shell covering a connector housing and a terminal.
2. Description of the Related Art
In a shielded connector, the connector is covered with a conductive cover (hereinafter referred to as "metal shell") so as to shield an internal conductor (terminal) from external electric fields, thereby preventing electromagnetic wave faults, i.e., noise. An example of such a shielded connector, in which an inner housing and an outer housing are separated from each other and assembled, will be described with reference to FIGS. 19 and 20. FIG. 19 is a longitudinal sectional view of a conventional shielded connector in which male and female connectors are fitted to each other, and FIG. 20 is a front view of a fitting surface of the male connector.
A shielded connector 1 is constituted by a male connector 3 and a female connector 5 which fit together. The male and female connectors 3 and 5 have substantially the same structure, and therefore the structure of the male connector 3 will be described by way of example.
An outer housing 7 is made from insulating resin and has an elliptic-cylindrical shape. A hollow portion 9 is defined in the outer housing 7. A circumferential wall 11 which has an elliptic-cylindrical shape is provided in the front portion of the outer housing 7 and projects therefrom. The circumferential wall 11 is fitted into a fitting groove 13 formed in the front portion of the female connector 5.
An inner housing 15 formed separately from the outer housing 7 is fitted into the hollow portion 9. A terminal reception chamber 17 is formed in the inner housing 15, and the terminal reception chamber 17 receives a terminal 23 which is connected to an insulated core 21 of a shielded wire 19. A cylindrical metal shell 25 is attached to the outer circumferential surface of the inner housing 15 to cover the inner housing 15. The rear portion of the metal shell 25 is connected to a shielded braid 27 of the shielded wire 19 by solderless contact, or the like. The inner housing 15 is covered with the metal shell 25, and fitted into the hollow portion 9, thus being installed in the outer housing 7. After installation, the metal shell 25 projects from the end surface of the inner housing 15. In the male connector 3, therefore, an electric connection portion 23a of the terminal 23, the metal shell 25 and the circumferential wall 11 project in this order from the center of the end surface. The shielded wire 19 is inserted through a waterproof seal member 29 so that the waterproof seal member 29 seals the gap between the hollow portion 9 and the shielded wire 19 in a water-tight fashion.
The male connector 3 is fitted to the female connector 5 which is constructed in substantially the same manner as the male connector 3, at their respective end portions. That is, when the male connector 3 is fitted into the female connector 5, the terminal 23 is inserted into a terminal 31 of the female connector 5 so that the inner housing 15 of the male connector 3 and an inner housing 33 of the female connector 5 are brought into contact at their end portions. At the same time, the circumferential wall 11 of the male connector 3 is inserted into a fitting groove 13 of the female connector 5. At that time, the metal shell 25 projecting over the top end surface of the male connector 3 is fitted into the inner circumference of a metal shell 35 projecting over the end surface of the female connector 5 in the same manner as the male connector 3.
Consequently, the inner housings 15 and 33 are covered with the metal shells 25 and 35 connected to the shield braid 27, so that inner conductors are shielded from an external electric field to prevent electromagnetic noise.
However, because the metal shell 25 surrounds the terminal 23 on the outer circumference of the inner housing 15 and projects therefrom into the conventional shield connector 1, the terminal 23 and the metal shell 25 are disposed parallel to each other and oppose each other through a short distance, or gap 37, between the end contact surfaces of the inner housings 15 and 33, when the male and female connectors 3 and 5 are fitted to each other. As a result, when a voltage is applied to the terminal 23, there is a possibility that discharge in the air will arise across the gap of 37 between the contact surfaces, and there is also the possibility that water may enter the gap 37 when the terminal 23 and the metal shell 25 are brought into an electrically conductive, thereby causing a short-circuit.
In addition, since the outer housing 7 and the inner housing 15 are formed separately from each other, there may be relative movement therebetween. Accordingly, the metal shells 25 and 35 may hit against each other when the connectors are fitted together, so that a smooth fit cannot be obtained.